Those guns tended to have fairly heavy triggers when compared to 1911s as primers back then weren't as sensitive as they are now and they needed a good whack to set off.
As far as a heavy trigger prevention NDs? I'm of the opinion that NDs are usually the result of a brain fart and there ain't any gadget that will help that.
Guns are like flying. There's lots of rules and adages, but the absolute is 'Don't f$%k up'. I've seen it placarded in more than one plane.